Recently, various attempts have been made to shield a telephone subscriber's number from unwanted calls (e.g., telemarketer calls). However, because of computer controlled sequential dialing of multiple numbers (which may include both listed and restricted telephone numbers in the network) is commonly performed by telemarketers, little, or if any, protection from telemarketers may be ensured. Restricted numbers are numbers that are not assigned to any subscriber; rather, these numbers are generated by the telecommunication system and temporarily used within the network for the purpose of routing calls. As such, calls placed by the telemarketers to these restricted numbers, albeit unintentionally, may unnecessarily use network facilities. This may thus put unnecessary burden on the network. Moreover, an anti-telemarketing program, employed by a network provider, uses the calling party identification of an incoming call to determine if the call is a telemarketing call by accessing a telemarketing database. The incoming call can be identified as a telemarketing call by direct correlation with a known telemarketing number. However, if the calling party number is suppressed or if it is not listed in the telemarketing database, the telemarketing call eventually reaches the telephone numbers that are restricted.
Therefore, there is a need to efficiently filter out calls made to restricted numbers and further routing calls to the appropriate subscribers by the network provider.